Exemplary embodiments generally relate to memory devices, and more particularly, exemplary embodiments relate to methods of operating nonvolatile memory devices and to methods of operating memory systems which include nonvolatile memory devices.
Nonvolatile memory devices are generally characterized by the retention of stored data even in the absence of supplied power. Examples of nonvolatile memory devices include read only memory (ROM), programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory (e.g., NOR type and NAND-type), and nonvolatile random access memory (RAM) such a phase-change RAM (PRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), ferroelectric RAM (FRAM0, or the like.
Despite the nonvolatile characteristics of nonvolatile memory devices, the integrity of data stored in the nonvolatile memory devices may deteriorate over time. In addition, when data is programmed in memory cells of the nonvolatile memory device, the programming action can alter the storage state (e.g., threshold state) of memory cells located adjacent to the programmed memory cells. These and other influences can lead to read errors in memory cells that where initially properly programmed.